1. Technical Field
The present invention relates to methods for producing liquid-ejecting heads having a liquid-resistant protective film in liquid channels thereof.
2. Related Art
Examples of liquid-ejecting heads include an ink-jet recording head including a diaphragm that defines pressure-generating chambers communicating with nozzle orifices from which ink droplets are ejected and piezoelectric devices that apply pressure to ink in the pressure-generating chambers by deform the diaphragm to eject ink droplets from the nozzle orifices.
One known liquid-ejecting head includes a passage-forming substrate having piezoelectric devices and a protective substrate bonded thereto. To connect electrodes of the piezoelectric devices to a wiring substrate having a drive circuit mounted thereon, specifically, a chip-on-film (COF) substrate, a through-hole is formed in the protective substrate, and leads are extended from the piezoelectric devices into the through-hole and are connected to the COF substrate in the through-hole (see, for example, JP-A-2009-255517 (page 6, FIG. 3).
According to one known method for producing a liquid-ejecting head, a protective film of a liquid-resistant (ink-resistant) material, such as tantalum pentaoxide, is formed on the inner surfaces of liquid channels, such as a manifold (reservoir), that come into contact with liquid by chemical vapor deposition (CVD) (see, for example, JP-A-2006-82529 (page 8, FIG. 6).
According to another known method, before the pressure-generating chambers are formed by etching, the through-hole is sealed off by laminating an organic film for protecting the piezoelectric devices from etchant as a protective tape with heat so that no etchant intrudes (see, for example, JP-A-2009-220507 (page 6, FIG. 7).
A protective film must be formed in complicated liquid channels to ensure sufficient liquid resistance. Therefore, the protective film is formed in the channels using a source gas containing the protective film component. The source gas, however, also forms the protective film on the leads in the through-hole as the source gas spreads into the through-hole. If the protective film, which is an insulating film, is formed on at least the portions of the leads to be connected to the wiring substrate, a continuity failure may occur between the leads and the wiring substrate upon connecting the wiring substrate to the leads. This decreases the yield and therefore makes it difficult to provide a method for producing liquid-ejecting heads at reduced production costs.